Cascade Operations in the order Application

Entities that have relationships to other entities often have dependencies
on the existence of the other entity in the relationship. For example, a line
item is part of an order, and if the order is deleted, then the line item
should also be deleted. This is called a cascade delete relationship.

In order, there are two cascade delete dependencies
in the entity relationships. If the Order to which
a LineItem is related is deleted, then the LineItem should also be deleted. If the Vendor to
which a VendorPart is related is deleted, then the VendorPart should also be deleted.

You specify the cascade operations for entity relationships by setting
the cascade element in the inverse (non-owning) side of
the relationship. The cascade element is set to ALL in
the case of Order.lineItems. This means that all persistence
operations (deletes, updates, and so on) are cascaded from orders to line
items.